1. Field of the Invention
The present invention relates to a Mobile Internet Protocol version 6 (MIPv6) network, and more particularly, the present invention relates to a method of exchanging traffic for a mobile node in a MIPv6 network.
2. Description of the Related Art
The present Internet is based upon Internet Protocol version 4 (IPv4). According to IPv4, a source sends a source address and a destination address on a packet to the Internet in order to transmit traffic to a destination. An IP address used in IPv4 is composed of 32 bits so that about 4 billion (4,000,000,000) hosts can access the Internet. However, the actual number of hosts capable of accessing the Internet is remarkably small because of special addressing, sub-netting and network address allocation. In addition, owing to the generalization of the Internet and an increase in multimedia traffic, unlike in the past, endeavors have been continuously made so that various devices such as mobile nodes, information home electronics and so on in addition to computers can access the Internet. Such mobile nodes and information home electronics such as televisions and refrigerators are of a vast number, and thus, IPv4 addresses have become insufficient for such devices to access the Internet. Accordingly, IPv6 technology was proposed to solve the insufficient IP addresses and complement the inefficiency of IPv4 so as to improve Internet performance.
IPv6 has a 128 bit address system. Thus, this address system has many more IP addresses than the 32 bit address system of IPv4. The address system increased to 128 bits also increases the contents of a routing table, which are essential for path determination at a router. This can increase the time consumed to find a suitable route. However, since the IPv6 address system has many more layers than the IPv4 address system, the increased time consumed to find a suitable route from the routing table is small.
Since IPv6 has improved performance over IPv4, IPv6 can solve Internet performance related problem owing to the rapid increase in Internet traffic and the generalization of multimedia traffic.
The IP address allocated to a host or node is composed of network identifier and host identifier. The network identifier is information for uniquely indicating a network to which the host is connected, and the host identifier is information for uniquely identifying the host in the corresponding network. The host allocated with the IP address generates a socket address by using the IP address and port number of a transmission layer, and establishes a connection to another host by using such socket information.
Therefore, once one host or host 1 has established a connection with another host or host 2, a constant IP address should be fixedly maintained to the host while the connection is established.
However, if one host connected to another host moves to another network, the network identifier should be changed, and the IP address allocated to the host must also be changed. Changing the IP address means changing the socket address, terminating all previously established connections, and thus, the host disadvantageously has to again attempt a connection.
In order to solve the problem of connection termination occurring when a host changes a network as above, the Internet Engineering Task Force (IETF) proposes a Mobile IPv6 (hereinafter referred to as ‘MIPv6’) protocol. The MIPv6 protocol proposes a method for enabling a Mobile Node (hereinafter referred to as ‘MN’) to continuously maintain previously-established connections even though the MN changes its location. That is, the MIPv6 protocol defines a mechanism by which even though the MN, which has connected to the Internet with has established connection to a Correspondent Node (hereinafter referred to as ‘CN’), changes its Access Point (AP), the MN can maintain a connection to the CN.
However, when an MN moves from an MIPv6 network to a new network, a predetermined time is consumed until the MN is provided with Internet access service from the new network. Such a time is referred to as hand-over latency, which includes a time period until recognizing that the MN has moved to the new network, a time period until composing a new address from the new network and a time period necessary for registering the composed new address.
Accordingly, when the MN has moved from the MIPV6 network, any packet sent during such hand-over latency is transmitted to the previous address, which the MN has accessed before hand-over, and thus the packet is lost. Thus, packet loss increases in proportion to hand-over latency.
In order to solve such problems and reduce hand-over latency, Hierarchical MIPv6 (hereinafter referred to as ‘HMIPv6’) and Fast hand-over for MIPv6 (hereinafter referred to as ‘FMIPv6’) have been proposed.
HMIPv6 defines a router having new functions so-called Mobile Anchor Point (MAP), in which a set of ARs having same MAP information is referred to as a MAP domain. When the MN moves within the MAP domain, address change is reported merely to the MAP to reduce binding update time and resultantly reducing hand-over latency.
When HMIPv6 is used, additional registration procedures can be omitted at hand-over in the same MAP domain. Thus, it is possible to reduce hand-over latency at hand-over in the same MAP domain. However, event this process cannot completely eliminate hand-over latency. That is, when the MN moves, hand-over latency occurs, so that the packets are still discarded. Thus, problems of packet loss still take place even in the HMIPv6 network.
As another solution to reduce hand-over latency, there is FMIPv6. FMIPv6 uses a system configuration of an MIPv6 network as is. FMIPv6 can previously process information before the movement of the MN to a new network in order to reduce hand-over latency as well as minimize packet loss.
However, if it takes a long time for the MN to move or if a binding update time is delayed so that a number of packets are buffered, then some of the packets are delivered to the MN before all of the buffered packets are delivered to the MN.
This can cause problems in that the packets are delivered to the MN in the wrong order. This wrong order of the packets can remarkably degrade the performance of an application program. When the packets are received in the wrong order, a receiving side of the packets generates an acknowledgment signal requesting packets in the correct order. This as a result causes a duplicated acknowledgment, and when a transmitting TCP receives 3 or more duplicated acknowledgments, the transmitting TCP promptly changes into a retransmission and recovery state. In this state, the transmitting TCP retransmits its own traffic and reduces the size of a congestion window. The reduced congestion window size also degrades the transmitting TCP performance.
Also, in case of UDP based multimedia traffic, packet loss or packet disordering considerably degrades quality.
Therefore, where the MN moves to a new network, a mechanism capable of preventing not only packet loss but also packet disordering is essential.